XTS DVR72XX-V User Manual page 135

Mixed ground: The mix ground consists of the feature of the one-point ground and multiple-point
ground. For example, the power in the system needs to use the one-point ground mode while the
radio frequency signal requires the multiple-point ground. So, you can use the following figure to
earth. For the direct current (DC), the capacitance is open circuit and the circuit is one-point ground.
For the radio frequency signal, the capacitance is conducive and the circuit adopts multiple-point
ground.
When connecting devices of huge size (the device physical dimension and connection cable is big
comparing with the wave path of existed interference), then there are possibility of interference when
the current goes through the chassis and cable. In this situation, the interference circuit path usually
lies in the system ground circuit.
When considering the earthing, you need to think about two aspects: The first is the system
compatibility, and the other is the external interference coupling into the earth circuit, which results in
system error. For the external interference is not regular, it is not easy to resolve.
3. Thunder proof ground method in the monitor system
The monitor system shall have sound thunder proof earthing to guarantee personnel safety and
device safety.
The monitor system working ground resistance shall be less than 1Ω.
The thunder proof ground shall adopt the special ground cable from the monitor control room to
the ground object. The ground cable adopts copper insulation cable or wire and its ground
section shall be more than 20mm2.
The ground cable of the monitor system can not short circuit or mixed connected with the strong
alternative current cable.
For all the ground cables from the control room to the monitor system or ground cable of other
monitor devices, please use the copper resistance soft cable and its section shall be more than
4mm2.
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